a) Field of the Invention
The present invention relates to a method of removing a coating film with laser beams and to a laser processing system suitable for use with the coating film removing method.
b) Description of the Related Art
Chemicals called methylene chloride highly toxic have been mainly used for removing a coating on an outer frame of a machine such as an airplane. Conventionally, this chemical is blown on the surface of a coating film to fragilize it and thereafter the coating film is scraped off from the outer frame surface of a machine.
Such a conventional method of removing a coating film has a low work efficiency and there are some problems on the collection and dumping of toxic waste.
It is an object of the present invention to provide a method of removing a coating film without using chemicals and to a laser processing system suitable for use with the coating film removing method.
According to one aspect of the present invention, there is provided a method of removing a coating film, comprising the step of: applying a laser light to a surface of an object to be processed and formed with a coating film thereon and removing at least an upper portion of the coating film through abrasion, by using an energy density variable optical system capable of applying the laser light to the surface of the object and varying an energy density of the laser light on the surface of the object.
If the energy density of radiated laser light is too low, abrasion does not occur, whereas if it is too high, the underlying material of the coating film is damages. There is therefore a proper range of the energy density when the coating film is removed through abrasion. By using the energy density variable optical system, the energy density can be set in the proper range.
According to another aspect of the present invention, there is provided a laser processing system comprising: a lens for converging or diverging a laser light and applying the laser light to a surface of an object to be processed; a lens support mechanism for supporting the lens and adjusting a height of the lens from the surface of the object in accordance with an external control signal; a height sensor for detecting the height of the lens from the surface of the object; control means for receiving an output signal from the height sensor and controlling the lens support mechanism so as to make constant the height of the lens from the surface of the object; and a first deflector disposed in an optical path of the laser light to be incident upon the lens, for moving a radiation position of the laser light along a first direction on the surface of the object, by changing a transmission direction of the laser light.
By changing the height of the lens from the surface of the object, the energy density of the laser light on the surface of the object can be changed. By moving the laser radiation position, the laser light can be applied to a broad area.
Since abrasion is used, the coating film on the surface of the object can be removed without using chemicals.